P11.18 Tumor treating fields (TTFields) treatment of spinal cord metastases

Abstract

Abstract BACKGROUND Tumor Treating Fields (TTFields) is an anti-mitotic cancer treatment approved for the treatment of Glioblastoma multiforme (GBM) and is currently also investigated in a phase III trial in 1–10 brain metastases from non-small cell lung cancer (METIS). Apart from spread to the brain, some cancer types, such as breast cancer, lung cancer, and melanoma, may lead to metastatic spread to the spinal cord. Previous studies have shown that reported transducer array layouts for the treatment of abdominal/pelvic tumors (e.g. pancreatic cancer), with one pair of arrays positioned on the anterior and posterior of the patient, and the second pair of arrays placed on each side of the thorax, yield therapeutically insufficient field intensities of <1 V/cm in the spinal cord. This finding probably results from the anatomical structure of the spine, consisting of the cerebrospinal fluid as a highly conductive layer, encased by a resistive bone structure that shunts the current delivered across the body by the arrays away from the spine. This simulation-based study aimed at resolving this challenge by identifying novel array layouts on the body that effectively deliver TTFields to the spine. MATERIAL AND METHODS For the simulations of the TTFields delivery to the spine, a human male 34 years old realistic computational model (DUKE v3.1 by ITI’S, Zurich) and the ZMT’s Sim4Life v4.0 electro-quasi-static solver was utilized. TTFields were simulated by imposing an alternating current with a current density of 200 mA/disk and a frequency of 150 kHz on the outer surfaces of the disks of each pair of arrays. RESULTS For one of the tested array layouts, a high electric field was shown to be induced within the spinal cord and surrounding CSF: Our calculations of mean field intensity within the spine and nerves from vertebrae T8-T9 at the top to L3-L4 at the bottom added up to 1.77 V/cm. This layout consisted of the placement of a pair of arrays on the back of the patient, with one array positioned above the section in the spine to which treatment would be delivered, and the other array positioned below the target section. Notably, the resulting electric field is directed along the spine in this setting (ie, vertically). CONCLUSION Our results demonstrate that treatment of the whole spinal cord and nerves in a single direction can be achieved by placing a pair of transducer arrays on the patient’s back: one array on the neck, and one at the bottom of the spine. For the development of an active treatment in the perpendicular direction, further studies need to be conducted.